Pacemakers, relied upon by many patients with irregular heart rhythms, are not built for children. Scrambling up trees, hanging from monkey bars, and even the simple act of growing make the device more likely to fail.
Roughly 1 in 15,000 children are born with congenital heart block, which causes an abnormally slow heart rate. The condition leads to lightheadedness, shortness of breath, and in serious cases, heart failure. Medications work in the short-term, but for children with more severe symptoms, pacemakers are the most reliable, durable treatment — though one fraught with risks. Traditional pacemakers have wires, or leads, that send electrical pulses to a slow-beating heart. The leads, however, do not mesh well with a growing body.
“The amount of physical activity that children do far exceeds a 60- or 70-year-old,” said Maully Shah, director of cardiac electrophysiology at the Children’s Hospital of Philadelphia. More than 70% of people with pacemakers are at least 65 years old. “None of these leads are really tested when they’re manufactured to accommodate for growth.”
Shah suspected that wireless pacemakers, which are implanted directly in the heart via catheter, might fare better in children’s bodies than the more traditional, wired devices. She and a team of pediatricians set out to look at the performance of wireless pacemakers in children with slow heartbeats across the globe. On Tuesday, they released the results in Circulation: Arrhythmia and Electrophysiology, a journal from the American Heart Association. They concluded that wireless pacemakers may work in children just as well as they do in adults, at least in the short term. But they concluded that until device makers create catheters that fit children’s veins, they can’t be widely used.
“Everything’s easier in a bigger person,” said Anne Dubin, head of the pediatric cardiology division at Stanford Medicine Children’s Health. “Once you get to smaller, more fragile blood vessels and tissues, your risks go up.”
The study is not an official clinical trial; but rather a retrospective analysis of real-world data. Physicians across 15 health centers implanted the wireless pacemakers in 63 children over a five-year period. Almost all of the children had successful implantations. The pacemaker remained effective over a follow-up period of 10 months, and in at least a third of patients, for over a year. Ten children experienced complications; most were due to minor bleeding, but three were major, including a blood clot and perforation of the heart.
At the time of the study, just one wireless pacemaker had earned FDA approval: Medtronic’s Micra pacemaker. The device makes up a minority of pacemaker implantations: Approximately 3 million Americans have pacemakers, and just over 100,000 patients have received the Micra device worldwide. It has risks, the most serious being poking tiny holes in the heart. Still, the technology is gaining traction, at least in adults. Another wireless pacemaker from Abbott received FDA marketing approval in 2022.
Shah, who was not consulting for Medtronic during the study but is a consultant for it now, sees promise in the device. But the catheters that are required to implant the pacemaker are often too large for children, and could easily cause grave complications.
“You’re working in a very small space, which is a pediatric heart,” Shah said. “The target is very small and the equipment is very large.”
Another issue is that the only way to extract the device is through surgery. When pacemaker batteries die, physicians can either implant an additional one or replace it completely. This is less of a big deal in older patients, who might require just one or two pacemaker replacements in their lifetime. But a child will go through many pacemakers in their lifetime. A small heart can fit only a finite number of pacemakers, and removing pacemakers surgically can cause serious harm.
“Whenever we do anything with children, we really have to think about their future,” Shah said. “Not just the implant at the time of the procedure, but how that is going to perform for a remainder of a child’s life.”
Dubin, who was not involved with the study, echoed Shah’s concerns about the current risks of implanting wireless pacemakers in children. She’s cautiously optimistic, but wants to see more long-term results before using the pacemakers at scale.
“I’ve already gotten several emails from colleagues saying, well, does this mean we’re going to use this across the board?” Dubin said. “No, it’s not enough for safety and efficacy yet.”
While Medtronic’s pacemaker fits in children, both Dubin and Shah said the device should be miniaturized even further. The device may be too big for some hearts, sticking through and causing leakiness in the heart’s right valve.
Dubin and Shah are both working to push the industry and the Food and Drug Administration to invest in pediatric device development in general. Few children require medical devices, so there’s little financial incentive for industry to invest in pediatric devices. Children make up a small sliver of their potential clientele. They are also hard to find, and thus enroll, in the large clinical trials the FDA requires of high-risk devices like pacemakers. That means pediatricians rely on using devices that have solely been tested on adults. Pediatric electrophysiologists use devices off-label constantly, Dubin said.
Shah plans to continue the study, increasing the cohort of patients and following them for a longer period of time. She hopes it will inspire device makers to catch up with the need for child-friendly devices.